Structure for mounting components

ABSTRACT

An acceleration sensor is disclosed which includes a capacitance-type acceleration detection element mounted on a ceramic base plate. The element comprises a movable electrode mounted between a pair of fixed electrodes. Acceleration of the sensor in a measurement direction causes the movable electrode to move relative to the fixed electrodes and the element has opposite ends in a direction perpendicular to the measurement direction. The acceleration detection element is mounted on the base at a first one of the opposite ends. Accordingly, the mounting surface of the acceleration sensor is parallel to the direction of acceleration to be detected. Thus the acceleration sensor can be surface-mounted on a printed board, and more be easily mounted in an automobile air bag control system or the like.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 08/778,538,filed on Jan. 3, 1997 now U.S. Pat. No. 6,305,223 which in turn is acontinuation of application Ser. No. 08/361,657, filed on Dec. 22, 1994now abandoned.

FIELD OF THE INVENTION

The present invention relates to an acceleration sensor, and moreparticularly to an automobile air bag control apparatus using anacceleration sensor.

BACKGROUND ART

One known acceleration sensor formed by layering glass or silicon isdescribed in JP-A-3-134570.

JP-B-4-55267 (equivalent to U.S. Pat. No. 4,679,434) discloses anacceleration sensor including a flat substrate having mounted thereon anacceleration detecting element and an electronic circuit for detecting achange in electrostatic capacitance of the acceleration detectingelement. The substrate is mounted in a metal housing. The accelerationsensor is fixed in place by means of screws to be inserted throughmounting holes formed through metal flanges in the housing.

The direction of acceleration to be detected by the acceleration sensoris perpendicular to the mounting surface of the acceleration sensor.Further, the use of the metal housing makes the acceleration sensorheavy. This structure results in various limitations on the mounting ofthe acceleration sensor in a system using the ensor.

In an air bag system, for example, a control unit of the air bag systemis usually mounted in a horizontal direction of a vehicle, whereas thedirection of acceleration to be detected by the acceleration sensor isthe same as a longitudinal direction of the vehicle.

Accordingly, in such an application, because of the fact that thedirection of acceleration to be detected by the acceleration sensor isperpendicular to the mounting surface of the acceleration sensor, it isnecessary to mount the sensor perpendicular to the longitudinaldirection of the vehicle. This necessitates complex mechanicalarrangements for the mounting of the sensor.

Moreover, because of the relatively large weight of the accelerationsensor itself, the sensor is liable to mechanically resonate (whichcauses an error in detection of the acceleration).

JP-A-5-340963 discloses an acceleration sensor in which the accelerationdetecting element is also mounted on a base plate such that thedirection of acceleration to be detected is perpendicular to the baseplate. The base plate is itself however mounted perpendicular to themetal base of the acceleration sensor housing, such that the directionof acceleration to be detected by the sensor is parallel to the mountingsurface of the sensor. However, this construction still results in acomplex and bulky device.

EP-B-0369352 discloses a capacitance-type accelerometer comprising threeparallel silicon plates, the central one of which includes a movableelectrode part. The plates are insulated from each other usingthermal-oxide films in all areas between the plates except thoseadjacent the movable electrode. There is no discussion of a method ofmounting the accelerometer.

It is an object of the present invention to provide an accelerationsensor which mitigates some of the above disadvantages.

SUMMARY OF THE INVENTION

In a first aspect the present invention provides an acceleration sensorincluding a base and an acceleration detection element of capacitancetype mounted on the base. The acceleration detection element has amovable electrode mounted adjacent a fixed electrode such thatacceleration of the sensor in a measurement direction causes the movableelectrode to move relative to the fixed electrode. The element furtherhas opposite ends in a direction perpendicular to the measurementdirection, and the acceleration detection element is mounted on the baseat a first one of the opposite ends.

The acceleration detection element being mounted at a first one of theopposite ends means that the first one of the ends is directed generallytowards the base. The end need not necessarily contact the base and insome embodiments the end is separated from the base by bonding material,such as an elastomeric adhesive, used to bond the acceleration detectionelement to the base.

Thus, the acceleration detecting element of the acceleration sensor isarranged so that the direction of acceleration to be detected by theacceleration sensor is parallel to a mounting surface of theacceleration sensor. Accordingly, the direction of acceleration to bedetected by the acceleration sensor mounted on the mounting surface isparallel to the surface, thereby making the mounting of the accelerationsensor easier.

Further, the acceleration detecting element may be airtightly sealed bya mounting surface or substrate on which the acceleration detectingelement is mounted, and a cover mounted on the substrate so as tosurround the acceleration detecting element, thereby reducing the weightof the acceleration sensor without use of a metal housing. Accordingly,even when the acceleration sensor is fixed to a printed board having alow mechanical rigidity, no resonance of the acceleration sensor occurs.

The element may comprise a movable electrode mounted between a pair offixed electrodes, with the element preferably having at least one endface which is substantially parallel to the direction of accelerationdetectable by motion of the movable electrode, wherein the element ismounted on the base such that the end or end face lies on the base. Theend face may be separated from the base by e.g. a fixing medium such asan adhesive.

Preferably, the movable electrode is supported by a flexible beam whichextends from the movable electrode towards the other of the oppositeends.

By locating the beam end of the movable electrode away from the base theeffect of vibrations on the acceleration detection element are reduced.

Preferably, the element has a pair of end faces which are eachsubstantially parallel to the direction of acceleration detectable bymotion of the movable electrode. A first one of the pair of end faces isthe most remote from the beam, and the element is mounted on the basesuch that the first end face lies on the base.

Preferably, the acceleration detection element includes at least oneelectrical connection terminal located at the other of the oppositeends.

Preferably the at least one electrical connection terminal forelectrical connection to the acceleration detection element is locatedin an end region of the acceleration detection element remote from theend or face which lies on the plate. Preferably the sensor includes atleast first and second electrical connection terminals for electricalconnection to the movable electrode and the fixed electroderespectively, and possibly a third electrical connection terminal forconnection to a second fixed electrode.

The above arrangements provide relatively easy access to the terminalsand allow for easier connection of e.g. wires thereto.

The acceleration detection element may be attached to the base byelastomeric adhesive, such as silicone rubber. This provides arelatively secure attachment whilst also giving some insulation of theacceleration detection element from external vibrations.

Preferably, the base is a ceramic base such as a ceramic plate and thesensor further includes signal processing means mounted on the base, thesignal processing means being electrically connected by electricalconnection means to the acceleration detection element, and the signalprocessing means being adapted to convert electrical information outputfrom the element into an electrical signal related to accelerationdetected by the element.

Advantageously, the ceramic base includes therein or thereon theelectrical connection means. In other words, the ceramic base may alsobe a circuit board having tracks or other circuit elements locatedthereon. Preferably, the electrical connection means connect the signalprocessing means to the movable electrode and the fixed electrode.

Preferably, the element includes at least first and second electricalconnection terminals for electrical connection to the movable electrodeand the fixed electrode respectively, and the terminals are connectedusing solder directly to the electrical connection means on the base.

In a second aspect, the present invention provides electrical apparatusincluding an acceleration sensor as described above mounted on a circuitboard using mounting means, wherein the mounting means also provideelectrical connection between the circuit board and the accelerationsensor.

In this way, a more compact packaging for the acceleration sensorincluded in the electrical apparatus may be provided. Such a packagingmay, for example, be a leadless chip carrier.

Preferably, the acceleration sensor is mounted on the circuit board suchthat the base (e.g. a base plate) is substantially perpendicular to thecircuit board. In this way the direction of acceleration detection maybe chosen to be either parallel or perpendicular to the circuit board asrequired.

In one embodiment, the movable electrode comprises a first semiconductorlayer which is mounted between first and second insulating layers, therebeing a pair of the fixed electrodes provided respectively on faces ofthe first and second insulating layers adjacent the movable electrode.The acceleration sensor further includes second and third semiconductorlayers each respectively mounted on a face of the first and secondinsulating layers remote from the movable electrode, with each of thefixed electrodes being connected to a different one of the second andthird semiconductor layers.

According to a third aspect, the present invention provides anacceleration sensor including an acceleration detection element mountedon a ceramic base, and signal processing means mounted on the base andelectrically connected by electrical connection means to theacceleration detection element. The base includes electrical tracksbeing part of the electrical connection means and the signal processingmeans are adapted to convert electrical information output from theelement to an electrical signal related to acceleration detected by theelement.

In this aspect, the invention is applicable to sensors havingacceleration elements of various different types, such as a strain gaugetype and a piezoelectric type, but it is especially applicable to thecapacitative type.

According to a fourth aspect, the present invention provides anautomobile air bag control system including an acceleration sensor orelectrical apparatus according to any of the above aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described by way ofnon-limitative examples with reference to the accompanying drawings. Inthe drawings:

FIG. 1 is a general sectional view of an acceleration sensor accordingto a first preferred embodiment of the present invention.

FIG. 2 is a sectional view in more detail of an acceleration detectingelement in the acceleration sensor of FIG. 1.

FIG. 3 is a sectional view showing a first mounting structure of theacceleration detecting element of FIG. 2.

FIG. 4 is a sectional view showing a modified mounting structure of theacceleration detecting element of FIG. 2.

FIG. 5 is a sectional view showing another form of the accelerationdetecting element and its mounting structure, which can be used in thesensor of FIG. 1.

FIG. 6 is a sectional view showing another configuration and mountingstructure of the acceleration detecting element of FIG. 5.

FIG. 7 is a sectional view showing another mounting structure of theacceleration detecting element of FIG. 2.

FIG. 8 is a sectional view showing yet another ounting structure of theacceleration detecting element of FIG. 2.

FIG. 9 is a sectional view of an acceleration sensor according to asecond preferred embodiment of the present invention.

FIG. 10 is a perspective view of an acceleration sensor according to athird preferred embodiment of the present invention.

FIG. 11 is a cross section taken along the line A-A′ in FIG. 10.

FIG. 12 is a sectional view of an acceleration sensor according to afourth preferred embodiment of the present invention.

FIG. 13 is a sectional view of an acceleration sensor according to afifth preferred embodiment of the present invention.

FIG. 14 is a perspective view of a triaxial acceleration sensoraccording to the present invention.

FIG. 15 is a sectional view of a control unit of an air bag systememploying an acceleration sensor according to an embodiment of thepresent invention.

FIG. 16 is a block diagram of an air bag control system.

DETAILED DESCRIPTION OF EMBODIMENTS

An acceleration sensor according to a first preferred embodiment of thepresent invention will now be described with reference to FIG. 1. FIG. 1is a general schematic sectional view of the acceleration sensor,according to the first preferred embodiment. This acceleration sensorincludes a ceramic substrate or base plate 109, an accelerationdetecting element 102 mounted on the ceramic substrate 109 for detectingacceleration having a direction parallel to the ceramic substrate 109(shown as direction of arrow A), an electronic circuit 103 (or signalprocessing means) mounted on the ceramic substrate 109 for convertinginformation output from the acceleration,detecting element 102 to anelectric signal according to the acceleration, and a ceramic cover 101bonded to the ceramic substrate 109 to thereby airtightly seal theacceleration detecting element 102 and the electronic circuit 103.

The acceleration detection element 102 has opposite ends 110 and 111 ina direction perpendicular to the measurement direction A. Theacceleration detection element is mounted on the base 109 at a first one110 of the opposite ends.

The wiring between the electronic circuit 103 and the outside of theacceleration sensor is effected by conductor patterns (or tracks) 104and 106 printed on the ceramic substrate 109. The conductor patterns 104and 106 are used also as soldering pads for fixing the ceramic substrate109 to a printed board 108 and for effecting wiring to the printed board108.

That is, as shown in FIG. 1, solders 105 and 107 are provided betweenthe conductor pattern 104 and the printed board 108 and between theconductor pattern 106 and the printed board 108, respectively, therebyeffecting the fixation of the ceramic substrate 109 to the printed board108 and the wiring to the printed board 108.

An acceleration detecting element formed by layering glass or siliconwill now be described with reference to FIG. 2. FIG. 2 shows a sectionalstructure of the acceleration detecting element adapted to detectacceleration in the direction of arrow A. The acceleration detectingelement is constructed of glass layers 204 and 208 and a silicon layer206. The central silicon layer 206 is formed with a beam 210 and amovable electrode 202 supported by the beam 210 and adapted to moveaccording to acceleration.

The upper and lower glass layers 204 and 208 are provided with fixedelectrodes 201 and 209, respectively, opposed to the movable electrode202. The fixed electrodes 201 and 209 and the movable electrode 202 areconnected to pads 203, 207, and 205, respectively, to effect electricalconnection to the outside.

Accordingly, when acceleration acts on the acceleration detectingelement in a direction of stacking of the layers 204, 206, and 208, themovable electrode 202 is moved in this direction of acceleration to bedetected. As a result, an electrostatic capacity or capacitance betweenthe movable electrode 202 and the fixed electrode 201 is changed, and anelectrostatic capacity between the movable electrode 202 and the fixedelectrode 209 is also changed. Thus, such changes in electrostaticcapacity are detected to thereby obtain an output according to theacceleration.

A first mounting structure of an acceleration detecting element 102according to the present invention will now be described with referenceto FIG. 3. The acceleration detecting element 102 shown in FIG. 3 is thesame as the acceleration detecting element shown in FIG. 2. To ensureparallelism and adhesive strength of the acceleration detecting element102 in fixing the acceleration detecting element 102 to a ceramicsubstrate 109, the length of the acceleration detecting element 102 inits layering direction is increased to increase an area of a bondingsurface of the acceleration detecting element 102 to be bonded to theceramic substrate 109. The bonding surface of the acceleration detectingelement 102 is bonded through an elastomeric adhesive e.g. siliconerubber 504 to the ceramic substrate 109. The bonding surface of theacceleration detecting element 102 is selected so that the beam 210 isfarthest from the bonding surface, thereby reducing any influence on theacceleration detecting element 102 due to a stress acting from theceramic substrate 109. The wiring from the acceleration detectingelement 102 to the ceramic substrate 109 is effected by wire bonding ofgold wires 501, 502, and 503 to the pads 203, 205, and 207,respectively.

A second mounting structure of an acceleration detecting elementaccording to the present invention will now be described with referenceto FIG. 4. FIG. 4 is a sectional view of the acceleration sensoraccording to the present invention. This acceleration sensor includes aceramic substrate 109, an acceleration detecting element 102 mounted onthe ceramic substrate 109 for detecting acceleration having a directionparallel to the ceramic substrate 109, an electronic circuit 604 mountedon the ceramic substrate 109 for converting information output from theacceleration detecting element 102 to an electric signal according tothe acceleration, and a ceramic cover (not shown) bonded to the ceramicsubstrate 109 to thereby airtightly seal the acceleration detectingelement 102 and the electronic circuit 604. The wiring between theelectronic circuit 604 and the outside of the acceleration sensor iseffected by a conductor pattern printed on the ceramic substrate 109.Further, the conductor pattern may be connected through a gold wire tothe ceramic cover by wire bonding.

Another form of an acceleration detecting element according to thepresent invention will now be described with reference to FIG. 5. First,the structure of the acceleration detecting element shown in FIG. 5 willbe described. The acceleration detecting element is constructed ofsilicon layers 802, 805, and 808 and glass layers 803 and 806. Thecentral silicon layer 805 is formed with a movable electrode 810 adaptedto move according to acceleration and a beam 809 for supporting themovable electrode 810. The glass layers 803 and 806 are provided withfixed electrodes 811 and 812, respectively, opposed to the movableelectrode 810.

Accordingly, when acceleration acts on the acceleration detectingelement in a direction of stacking of the layers, the movable electrode810 is moved in this direction of acceleration to be detected. As aresult, an electrostatic capacity between the movable electrode 810 andthe fixed electrode 811 and an electrostatic capacity between themovable electrode 810 and the fixed electrode 812 are changed. Thus,such changes in electrostatic capacity are detected to thereby obtain anoutput according to the acceleration.

The wiring from the fixed electrodes 811 and 812 to the outside iseffected by the silicon layers 802 and 808 and pads or electricalconnection terminals 801 and 807 provided thereon. The wiring from themovable electrode 810 to the outside is effected by a pad 804 providedon the silicon layer 805.

The acceleration detecting element is fixed to a ceramic substrate 109by soldering of the pads directly to the substrate using solder 814, 815and 816. Thus the ceramic substrate is also used as a circuit board.

Further, the length of the acceleration detecting element in itslayering direction is increased to thereby increase an area of a bondingsurface and accordingly increase a bonding strength of the accelerationdetecting element to the ceramic substrate 109.

In addition, the bonding surface of the acceleration detecting elementis selected so that the beam 809 is farthest from the bonding surface,thereby reducing an influence of stress acting from the ceramicsubstrate 109 to the acceleration detecting element.

FIG. 6 shows a mounting structure for an acceleration detecting elementsimilar to that shown in FIG. 5. However in the embodiment illustratedin FIG. 6. the electrical connection terminals 801, 804 and 807 areprovided on the surfaces of the silicon layers 802, 805 and 808 on theface of the element remote from the ceramic plate 109. The accelerationdetecting element is fixed to the ceramic plate 109 using siliconerubber adhesive 813 and, although not shown, wiring from theacceleration detecting element to the ceramic plate 109 is effected by awire bonding of gold wires to the pads 801, 804 and 807.

A fifth mounting structure of an acceleration detecting element 102according to the present invention will now be described with referenceto FIG. 7. The acceleration detecting element 102 shown in FIG. 7 is thesame as the acceleration detecting element shown in FIG. 2. Theacceleration detecting element is bonded through silicone rubber 906 toa ceramic substrate 907. Conductor patterns 904 and 908 formed on theceramic substrate 907 are connected through solders 905 and 909 to aceramic substrate 109. Thus, the acceleration detecting element 102 isfixed to the ceramic substrate 109. The wiring from the accelerationdetecting element 102 to the ceramic substrate 109 is effected by wirebonding of gold wires 901, 902, and 903 from pads 203, 205, and 207 tothe conductor pattern 904 and by the solder 905 from the conductorpattern 904 to the ceramic substrate 109.

A sixth mounting structure of an acceleration detecting element 102according to the present invention will now be described with referenceto FIG. 8. The acceleration detecting element 102 shown in FIG. 8 is thesame as the acceleration detecting element shown in FIG. 2. In thismounting structure, a vertical member 1005 is provided on a ceramicsubstrate 109, and the acceleration detecting element 102 is bondedthrough silicone rubber 1004 to the vertical member 1005. Gold wires1001, 1002, and 1003 are connected between pads 203, 205, and 207 andthe vertical member 1005. According to this mounting structure, theprovision of the vertical member 1005 standing on the ceramic substrate109 improves the vertical accuracy of mounting of the accelerationdetecting element 102.

An acceleration sensor according to a second preferred embodiment of thepresent invention will now be described with reference to FIG. 9. FIG. 9is a sectional view of the acceleration sensor according to the secondpreferred embodiment, adapted to detect acceleration in the direction ofarrow A. This acceleration sensor includes a ceramic substrate 1101, anacceleration detecting element 1103 mounted on the ceramic substrate1101 for detecting acceleration having a direction perpendicular to theceramic substrate 1101, an electronic circuit 1104 mounted on theceramic substrate 1101 for converting information output from theacceleration detecting element 1103 to an electric signal according tothe acceleration, and a ceramic cover 1102 bonded to the ceramicsubstrate 1101 to thereby airtightly seal the acceleration detectingelement 1103 and the electronic circuit 1104.

Electrical connection between the electronic circuit 1104 and theoutside of the acceleration sensor is effected by a conductor pattern1105 printed on the ceramic substrate 1101. The conductor pattern 1105and another conductor pattern 1107 formed on the ceramic cover 1102 areused also as soldering pads for fixing the ceramic substrate 1101 andthe ceramic cover 1102 to a printed board 108. That is, as shown in FIG.9, solders 1106 and 1108 are provided between the conductor pattern 1105and the printed board 108 and between the conductor pattern 1107 and theprinted board 108, respectively.

An acceleration sensor according to a third preferred embodiment of thepresent invention will now be described with reference to FIGS. 10 and11. FIG. 10 is a perspective view of the acceleration sensor accordingto the third preferred embodiment, and FIG. 11 is a cross section takenalong the line A-A′ in FIG. 10. This acceleration sensor includes aceramic substrate 1207, an acceleration detecting element 1301 mountedon the ceramic substrate 1207 for detecting acceleration having adirection perpendicular to the ceramic substrate 1207, an electroniccircuit 1302 mounted on the ceramic substrate 1207 for convertinginformation output from the acceleration detecting element 1301 to anelectric signal according to the acceleration, and a ceramic cover 1201bonded to the ceramic substrate 1207 to thereby airtightly seal theacceleration detecting element 1301 and the electronic circuit 1302.

The acceleration sensor is adapted to be mounted on a control unit of anair bag system or the like by using mounting holes 1202 and 1203 formedthrough the ceramic substrate 1207 and the sensor detects accelerationin the direction of arrow A. Further, leads 1204, 1205, and 1206 aremounted on the ceramic substrate 1207 to effect easy wiring to externalequipment.

An acceleration sensor according to a fourth preferred embodiment of thepresent invention will now be described with reference to FIG. 12. FIG.12 is a sectional view of the acceleration sensor according to thefourth preferred embodiment adapted to detect acceleration in thedirection of arrow A. This acceleration sensor includes a ceramicsubstrate 1405, an acceleration detecting element 1402 mounted on theceramic substrate 1405 for detecting acceleration having a directionperpendicular to the ceramic substrate 1405, an electronic circuit 1403mounted on the ceramic substrate 1405 for converting information outputfrom the acceleration detecting element 1402 to an electric signalaccording to the acceleration, and a metal cover 1401 bonded to theceramic substrate 1405 to thereby airtightly seal the accelerationdetecting element 1402 and the electronic circuit 1403. The accelerationsensor is adapted to be mounted on a side surface of a control unit ofan air bag system or the like by using mounting holes 1404 and 1406formed through the metal cover 1401.

An acceleration sensor according to a fifth preferred embodiment of thepresent invention will now be described with reference to FIG. 13. FIG.13 is a sectional view of the acceleration sensor according to the fifthpreferred embodiment. This acceleration sensor includes a ceramicsubstrate 1509, an acceleration detecting element 1502 mounted on theceramic substrate 1509 for detecting acceleration having a directionperpendicular to the ceramic substrate 1509, an electronic circuit 1503mounted on the ceramic substrate 1509 for converting information outputfrom the acceleration detecting element 1502 to an electric signalaccording to the acceleration, and a ceramic cover 1501 bonded to theceramic substrate 1509 to thereby airtightly seal the accelerationdetecting element 1502 and the electronic circuit 1503.

The acceleration sensor is mounted on a printed board 1508 by fixing theceramic substrate 1509 through conductor patterns 1504 and 1506 formedon the ceramic substrate 1509 and solders 1505 and 1507 to the printedboard 1508. The conductor patterns 1504 and 1506 are used also as wiringmeans for wiring the electronic circuit 1503 to the printed board 1508.

In the acceleration sensor according to this preferred embodiment, amounting surface of the acceleration sensor is perpendicular to thedirection of acceleration to be detected (arrow A). Accordingly, theacceleration sensor can be surface-mounted on any systems as applied tocontrol vibration of a vehicle, e.g. other than an air bag system.

A triaxial acceleration sensor according to the present invention willnow be described with reference to FIG. 14. This triaxial accelerationsensor includes a ceramic substrate 1604 and three accelerationdetecting elements 1601, 1602, and 1603 mounted on the ceramic substrate1604 so that the directions of accelerations to be detected by theacceleration detecting elements 1601, 1602, and 1603 are perpendicularto one another (shown by arrows D, B and C respectively).

Although not shown in FIG. 14, the triaxial sensor may also include anelectronic circuit and a ceramic cover. The acceleration detectingelements 1601, 1602, and 1603 detect acceleration in mutuallyperpendicular directions and the electronic circuit converts informationoutput from the acceleration detecting elements 1601, 1602, and 1603 toelectric signals, thereby detecting acceleration in any of the threeperpendicular directions.

An air bag system employing the acceleration sensor according to thepresent invention will now be described with reference to FIGS. 15 and16. FIG. 15 is a sectional view of a control unit of the air bag systemshowing direction of acceleration detection by arrow A, and FIG. 16 is ablock diagram of the air bag control system.

The air bag system is constructed of a case 1701 and a printed board1704 mounted in the case 1701. An acceleration sensor 1703 and anelectronic circuit 1702 are mounted on the printed board 1704. The airbag system is characterized in that the acceleration sensor 1703 issurface-mounted on the printed board 1704.

Furthermore, the acceleration sensor 1703 is fixed at a position near afixed portion of the printed board 1704 fixed to the case 1701, so as toreduce any influence due to resonance of the printed board 1704.

Referring to FIG. 16, the air bag system is composed of an accelerationsensor 1801 for detecting acceleration of collision of a vehicle, amicrocomputer 1802 for computing the magnitude of the collision from anoutput from the acceleration sensor 1801 and determining whether or notan air bag should be expanded, and a drive circuit 1803 for amplifyingan output from the microcomputer 1802 to drive the air bag (output E).

Although the acceleration sensors herein described with reference to thedrawings are of an electrostatic capacitance type, any other types ofacceleration sensor such as a strain gauge type or a piezoelectric typemay be used in the invention where appropriate.

While the invention has been illustrated by specific embodiments, it isnot limited to those embodiments, and extends to all modifications andimprovements in accordance with the concept of the invention.

What is claimed is:
 1. A structure for mounting electronic componentscomprising: a housing including a ceramic substrate; conductor patternsformed on the housing; and electronic components including anacceleration detector which is bonded on the inside of the housing andis connected to the conductor patterns, wherein; the housing is composedof a ceramic substrate and a ceramic cover.
 2. A structure for mountinga housing containing electronic components therein comprising: ahousing; conductor patterns formed on the housing; a gold connection ona surface of the conductor patterns; and a base board for mounting thehousing thereon, the housing being soldered on the base board andelectrically connected thereto at portions where the conductor patternsare formed.
 3. A structure for mounting a housing containing electroniccomponents therein according to claim 2, wherein said gold connection isa gold film having a thickness of more than 0.07 μm.
 4. A structure formounting a housing containing electronic components therein according toclaim 3, wherein the conductor patterns further include a base film ofsilver or a silver alloy on the housing, the gold film being formed onthe base film.
 5. A structure for mounting a housing containingelectronic components therein according to claim 3, wherein theelectronic components comprise an acceleration detector and anelectronic circuit generating an electrical signal in accordance withthe acceleration detected by said acceleration detector, wherein saidelectronic circuit is electrically connected to said conductor patternsand is placed in conduction with said base board through said conductorpatterns.
 6. A structure for mounting a housing containing electroniccomponents therein according to claim 5, wherein a processing circuit isprovided on said base board to process said electrical signal and saidprocessing circuit is electrically connected to said electronic circuitthrough said conductor patterns.
 7. A structure for mounting a housingcontaining electronic components therein according to claim 6, whereinsaid acceleration detector comprises a weight and a beam supporting saidweight formed on a silicon plate.
 8. A structure for mounting a housingcontaining electronic components therein according to claim 7, whereinsaid housing is soldered on said base board so that said silicon plateis substantially perpendicular to said base board.
 9. A structure formounting a housing containing electronic components according to claim5, wherein said housing is composed of ceramic and said accelerationdetector and said electronic circuit are hermetically sealed internallyof said housing.
 10. A structure for mounting a housing containingelectronic components according to claim 5, wherein said housing iscomposed of a ceramic substrate and a ceramic cover.